Add basic FreeArc device support

[schdro]

Uses SPP port 16.
Quite similar to 4i. But featuring also some new values/features.

Fixes #85

Unfinished:

• The two "fake" equalizer settings are little vague. But left as is.
• Also unclear to me if other devices -- e.g. by firmware update -- meanwhile also support newly added values e.g. for "Next+Prev" swipe action, spotted new "dynamic" equalizer setting, or for starting assistant functions via long tap.
• For devices with combined (unsplit) swipe, the swipe setting UI likely disappears, as those would not have "swipe_gesture_left". But presumably this is already issue for devices using unsplit long tap handler within gesture.py, and needs some adaptations there. OTOH, likely OFB<1.0 still is under preparation.

So this is for now some draft, which works for my local FreeArc, but needs realignments on overall integration. Such are also difficult to judge without owning other devices.

[melianmiko]

Thank you for your work, will reciew your code in a few days.

The two "fake" equalizer settings are little vague. But left as is.

Fun fact, they're fake also in AI Life, even on devices that officialy have this presets, they're send as custom preset. And I've dumped this presets from (probably) 5i.

Also unclear to me if other devices -- e.g. by firmware update -- meanwhile also support newly added values e.g. for "Next+Prev" swipe action, spotted new "dynamic" equalizer setting, or for starting assistant functions via long tap.

This can be found only by testing on real devies, if they don't, best solution would be hide this options for other models. I'll try on my 5i and FreeLace Pro 2 in a few days, but think it won't work.

For devices with combined (unsplit) swipe, the swipe setting UI likely disappears, as those would not have "swipe_gesture_left"

Will also look later, anyway, rework UI a bit isn't a big deal. Anyway I'm thinking about rewriting UI from pure Qt to QML for better compatibility and integration with KDE

[schdro]

Meanwhile from further testing also removed sound quality feature handler from arc.py again. It seemed that this could be set (likely because of shared firmware?). But it had no effect. From data sheet, FreeArc has no LDAC/aptx codec. Also could not find such in original settings.